Some Unusual Side Groups

The chiral reagent 122 was proposed for derivatization of enantiomeric mixtures of amino acids. Good HPLC separations were obtained for the diasteroisomer derivatives of a series of amino acids, including some unusual a-amino acids with long or bulky side chains, aryl and hetaryl groups, and -substituted /J-amino acids297. 

Based on spectroscopic properties, mainly electron paramagnetic resonance (EPR), the active sites of copper proteins have been classified into three groups, types I, II, and III. This nomenclature was originally applied to blue oxidases to distinguish the four copper ions contained in these proteins. The original classification has been extended to the copper sites of other proteins. The recent increase in structural information on the copper sites in proteins has, however, revealed greater diversity in the type of copper site. For instance, the type III and type II sites in ascorbate oxidase are in close proximity, forming a trinuclear site, in which all three copper ions are essential for the reactivity. Some proteins, once believed to contain a copper site with normal spectroscopic properties, and thus referred as type II, have been shown to contain copper coordinated by an unusual side chain. Therefore, in this review, new nomenclature is used to classify the copper sites more precisely with respect to their structural features and spectroscopic properties. The definitions are as follows ... 

Polyphosphazenes are some of the most diverse inorganic type polymers known. The presence of phosphorus and nitrogen atoms in the backbone and the unusual method of synthesis, with which an almost infinite variety of side groups and combinations of (fifferent side groups can be linked to the backbone, confer to the polymers a variety of interesting properties (1-3). Therefore, the applications of polyphophazenes can be very broad, and includes flame retardent materials, high performance elastomers, optical and electronic materials, biomedical materials etc.(3-8). The application potentials of some elastomers included aerospace, marine, oil exploration and industrial fields. However, despite to the hundreds of the polyphosphazenes synthesized, they are still expensive to produce and very few of them have been commercialized (6). 

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